Laminate and method for making laminate

ABSTRACT

A method of insert molding comprises placing in a first mold a curable rubber composition comprising a reactive species; placing on a surface of the rubber composition a first thermoplastic material in a film or layer comprising a group reactive with the reactive species of the rubber composition; curing the rubber composition in the mold to form a first molded article of cured rubber having a first thermoplastic material layer covalently bonded through reactive of the reactive species and the group; placing the first molded article as an insert into a second mold, the cured rubber contacting an inside surface of the second mold and the thermoplastic layer facing into the second mold cavity; closing the second mold and injecting into the second mold a second thermoplastic material that to form a second molded article comprising the first molded article thermally welded and/or covalently bonded to the second thermoplastic material.

FIELD

The present disclosure relates to methods of adhering together layers ofrubber and thermoplastic polymer during insert injection molding andmolded articles containing both rubber and thermoplastic materials.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may not constitute prior art.

It is sometimes desirable to combine two polymeric materials into anarticle to take advantage of properties of each of the materials, suchas an elastic material and an inelastic material or a thermoplasticmaterial and a thermoset material. Lyden et al., U.S. Pat. Nos.5,906,872, 5,843,268, 5,786,057, and 5,709,954 disclose chemicallybonding a rubber and a plastic in making, for example, a footwearoutsole, by molding the plastic into a first piece and then molding andcuring the rubber in the presence of the molded plastic piece. It isimportant in this process for the melt temperature of the plastic to behigher than the rubber curing temperature to prevent deformation of themolded plastic insert piece during rubber molding and curing. There aremany plastics unsuitable for this process due to lower melting orsoftening points than can withstand the rubber processing conditions.

Hernandez, US Patent Application Publication No. 2004/0000255 describesforming a foamed cushion pad from a mixture of SBS(styrene-butadiene-styrene copolymer), EVA (ethylene-vinyl acetatecopolymer), filler, curing agent, and a blowing agent, then insertingthe foam pad into a recess of the upper mold in forming an outsole. Theoutsole compound is 50-100 wt % SBS and 45-60 wt % EVA, filler, curingagent, and a processing oil. Peroxide is used as curing agent for boththe cushion pad and the outsole.

Lorenzin, US Patent Application Publication No. 2004/0026820 describes aprocess for manufacturing a sole in which a vulcanized rubber (NBR)containing a small amount of an acrylic resin with hydroxylfunctionality and a hydrocarbon resin is cured in a mold to form a treadsole. A two-component polyurethane is then injected and cured to form amid-sole. The publication postulates “mating” because the rubber surfaceretains “many free bonds” after vulcanization, impliedly from thehydroxyl acrylic resin.

Finally, Krajcir, U.S. Pat. No. 6,007,748 discloses a method of making amolded laminate sole for footwear in which a first heat curable materialis placed in a mold, a second polymerizable material is injected to fillthe remainder of the mold cavity, and polymerization of the secondmaterial generates heat that cures the first material. The documentdiscloses foamable, polymerizable polyurethane, synthetic rubber, andPVC as suitable for the second material and mentions vulcanizable rubberas the first material.

There remains a need for an effective way to assure good adhesion of athermoplastic layer to a cured rubber layer in a composite of suchlayers, such as is used as a sole assembly for footwear, without thedisadvantages of using adhesives or the limitations on selection ofthermoplastics used as an insert in molding rubber compositions.

SUMMARY

A method of insert molding comprises placing in a first mold a curable(i.e., still uncured) rubber composition comprising a reactive species;placing on a surface area (that is, on an area facing into the moldcavity) of the rubber composition a thermoplastic film or layercomprising a group reactive with the reactive species of the rubbercomposition; curing the rubber composition in the mold to form a firstmolded article of cured rubber having a thermoplastic layer covalentlybonded through reaction of the reactive species and the group; placingthe first molded article into a second mold, the cured rubber contactingan inside surface of the second mold and the thermoplastic layer facinginto the second mold cavity; closing the second mold and injecting intothe second mold a thermoplastic material that is at a temperature abovethe softening point of the thermoplastic layer to form a second moldedarticle comprising the first molded article. The reactive species may becovalently attached to a polymer of the rubber composition, may be areactive group of a compound that covalently bonds to the rubber duringcuring of the rubber composition, or may be a reactive group generatedduring curing of the rubber that covalently attaches the thermoplasticlayer to the cured rubber.

In one embodiment of this method, the reactive species in the rubbercomposition is a peroxide or sulfur curing agent and the thermoplasticpolymer group reactive with the reactive species is an ethylenicallyunsaturated group, carbonyl group, urethane group, urea group,thiocarbonyl group, cyano group, strained hetero ring such as an epoxideor aziridine ring, or a reactive alpha hydrogen.

In a second embodiment, the thermoplastic material comprises a couplingagent such as an aminosilane, zirconate, or titanate coupling agentreactive with a group in the rubber composition.

A method of preparing a molded article comprises placing in a mold arubber insert having a surface layer comprising a thermoplasticelastomer, wherein a rubber surface of the insert is adjacent to a moldsurface and the surface layer of the insert extends into a mold cavity;closing the mold and injecting into the mold a thermoplastic material;and cooling the thermoplastic material to form a molded articlecomprising the insert.

These methods make composite thermoplastic/rubber articles without usingadhesives, providing a simpler process and potentially more durablearticle. Such articles may be used in the manufacture of footwear, forexample. One article provided is an outsole for footwear, in which oneor more rubber elements are incorporated at desired locations. In anembodiment of this method and article, an outsole of an article offootwear is prepared comprising a rubber material and a thermoplasticmaterial bonded to one another through an intervening thermoplasticlayer, the intervening thermoplastic layer being covalently bonded tothe rubber layer. The rubber is located in one or more regions toprovide desirable physical and mechanical properties to the outsole. Asan example, the rubber may be located in specific areas along the lengthof the outsole to improve traction during use of the footwear, or therubber may be inserted in an area across the width of the outsole toincrease flexibility at that point of the outsole. Wherever located, theadhesion between the thermoplastic and rubber elements of the outsolemust be strong.

Further areas of applicability will become apparent from the descriptionprovided herein. It should be understood that the description andspecific examples are intended for purposes of illustration only and arenot intended to limit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.

FIG. 1 is a perspective view of a shoe with outsole prepared accordingto this disclosed method;

FIG. 2 is a cross-sectional view along line 2-2 of FIG. 1;

FIG. 3A is a plan view of a footwear outsole showing a rubber segmentlocated in an area underlying the toes bonded to two thermoplasticportions comprising the rest of the outsole; FIG. 3B is a partialcross-sectional view along line 3B-3B of FIG. 3A; FIG. 3C is analternative embodiment of a partial cross-sectional view along line3B-3B of FIG. 3A; and

FIG. 4A is a plan view of an alternate embodiment of a footwear outsolehaving wedge-shaped rubber segments bonded to a thermoplastic outsole atcorresponding wedge-shaped notches therein so as to enhance theflexibility of the footwear outsole in at least one select area andalong at least one select line of flexion such as lines B-B and C-C;FIG. 4B is a partial cross-sectional view along line C-C of FIG. 4A.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is notintended to limit the disclosed invention, its application, or its uses.

In a first embodiment of the method, a curable rubber composition isplaced in a first mold and a film or layer of a first thermoplasticcomposition is placed on a surface of the rubber composition, then themold is closed and the rubber composition is cured to form a moldedrubber article having at a surface a covalently bonded layer of thefirst thermoplastic composition. Alternatively, the mold may be closedafter the rubber composition is positioned, and the thermoplasticcomposition injected into the mold, then the mold heated to cure therubber and cause covalent bonding of the thermoplastic composition tothe rubber. The uncured rubber composition comprises a reactive speciesthat reacts during the rubber curing cycle with a group of thethermoplastic composition to covalently bond the thermoplastic layer tothe molded rubber article.

Curable rubber compositions contain a rubber resin and a curing agent,and may also contain an accelerator, a reinforcing material or fillersuch as silica, a processing oil for easier compounding and processing,and other optional additives. The rubber composition may contain curablenatural or synthetic rubber, or mixtures of curable rubbers. The rubbermaterials may comprise homopolymers of conjugated diene monomers,copolymers of two or more conjugated dienes and copolymers of one of thedienes with a monoalkenyl arene, preferably in which the copolymer haspredominantly conjugated diene units. The conjugated dienes preferablycomprise from 4 to 8 carbon atoms. Nonlimiting examples of suitableconjugated diene monomers include butadiene, isoprene,2,3-dimethyl-1,3-butadiene and piperylene. Nonlimiting types of rubberthat may be used include styrene-butadiene rubber (SBR), polyisoprenerubbers including natural rubber (NR) and isoprene rubber (IR),polybutadiene rubber (BR), acrylonitrile-butadiene rubber (NBR),carboxylated nitrile rubber (XNBR), polychloroporene (neoprene),bromobutyl rubber, chlorosulfonated polyethylene, silicone rubber,ethylene-propylene rubbers (EPR, EPDM), and combinations of these. Otherelastomers useful as rubber materials in the present invention includeblock copolymers comprising a relatively inelastic or “hard” phase and arelatively elastic or “soft” phase. The preparation of such blockcopolymers is known. See U.S. Pat. Nos. 4,174,358; 4,292,414; 4,783,503;4,795,782; 4,797,447; 4,868,243; 4,868,245; 4,882,384; 4,898,914; and4,906,687, the disclosures of which are herein incorporated byreference.

The rubber material may be chemically modified to facilitate thechemical bond between the first thermoplastic material and the rubbermaterial. The rubber material may be modified by addition of a modifyingagent to the base rubber that imparts the reactive species to the rubbermaterial. The mode of such addition may be, for example, by means of asurface preparation or by dispersion within the rubber material. Thereactive species may be incorporated into the rubber material is byreaction of, for instance, hydroxyl, carboxyl, amino, ester, ether andthe like groups of the modifying agent. The modifying agent may reactwith the polymeric backbone of the rubber material or may react with aterminal group. For example, maleic anhydride, maleic acid, fumaricacid, or another unsaturated acid or anhydride may be added to therubber to form an adduct with the ethylenic unsaturation present in therubber material and iinpart carboxylic acid or anhydride functionalityto the rubber that can be reacted under appropriate conditions with agroup of the first thermoplastic composition to produce a chemical bondbetween the rubber and the first thermoplastic composition. See U.S.Pat. Nos. 3,887,527; 4,292,414; 4,427,828; 4,429,076; 4,578,429;4,657,970; and 4,795,782, the disclosure of which are herebyincorporated by reference.

Reactive functionality, for example, carboxyl or anhydride groups, maybe incorporated into the alkenylarene potion of the rubber material,such as those having no ethylenic unsaturation, or into both thealkenylarene portion and other portions thereof having ethylenicunsaturation. See U.S. Pat. Nos. 4,783,503; 4,797,447; 4,898,914; and4,906,687, the disclosures of which are herein incorporated byreference.

The rubber material may be foamed or blown by use of foaming or blowingagents. Physical foaming and blowing agents function as gas sources byundergoing a change in the phase state. Suitable physical blowing andfoaming agents may be selected from the group consisting of aliphatichydrocarbons and their chloro-and fluoro-derivatives. Typical foamingand blowing agents may be selected from the group consisting of isomersof pentane, hexane, heptane, fluorocarbons, trichlorofluoromethane,dichlorodifluoromethane, dichlorotetrafluoroethane,monochlorodifluoromethane, methylene chloride, carbon dioxide, water andnitrogen. For example, water is a used as a blowing agent formicrocellular polyurethane. Chemical foaming and blowing agents producea gas via a chemical reaction. Suitable chemical foaming and blowingagents may be selected from the group consisting of sodium bicarbonate,dinitrosopentamethylene-tetramine, sulfonyl hydroxides, azodicarbonamide, p-toluenesulfonyl semicarbazide, 5-phenyltetrazole,diisopropylhydrazodicarboxylate and sodium borohydrite. The thermaldecomposition of the foaming or blowing agents can be lowered throughaddition of activators or accelerators. Water also may be employed as ablowing or foaming agent in the case of polyurethane-containingmaterials. The rubber material may be foamed or blown using thesefoaming and blowing agents by methods known in the art.

The rubber material may be modified by addition of functional moietieswhich provide carboxylic acid, amide, hydroxyl and other reactivefunctional groups. In some cases, preferred functional groups may beselected from the group consisting of amino groups, hydroxyl groups,thiol groups, carboxyl groups, anhydride groups, isocyanate groups,epoxide groups, silane groups, and groups derived therefrom such asurethane groups, ester groups, amide groups, and metal carboxylategroups.

Typically, solid rubber materials useful in footwear applications have ahardness within the range of 30-90 Shore A Durometer, per ASTM D-2240.Preferably, the solid rubber materials have a hardness within the rangeof from about 40-80 Shore A Durometer, and more preferably within therange of from about 50-70 Shore A Durometer. The modulus at 300%elongation of solid rubber materials useful in the footwear applicationsis from about 10 to about 90 kg/cm², per ASTM D-412. Preferably, themodulus at 300% elongation is within the range of from about 20-80kg/cm², and more preferably from about 30 to about 70 kg/cm².

The hardness of a foamed or blown rubber material useful in the presentmethods and articles typically ranges from about 20 to about 90 Asker CDurometer, and the modulus of the foamed or blown rubber typicallyranges from about 10 to about 90 kg/cm² at 150% elongation, from about10 to about 80 kg/cm² at 200% elongation and from about 10 to about 60kg/cm² at 300% elongation, per ASTM D-412. Preferably, the hardness of afoamed or blown rubber material ranges from about 50 to about 80 Asker CDurometer, and more preferably from about 40 to about 70 Asker CDurometer. Preferably, the modulus of the foamed or blown rubber rangesfrom about 10 to about 80 kg/cm² at 150% elongation, from about 20 toabout 70 kg/cm² at 200% elongation and from about 10 to about 50 kg/cm²at 300% elongation. More preferably, the modulus of the foamed or blownrubber ranges from about 20 to about 60 kg/cm² at 150% elongation, fromabout 30 to about 60 kg/cm² at 200% elongation and from about 20 toabout 40 kg/cm² at 300% elongation.

In preferred embodiments, the rubber resin contains less than 50% byweight natural rubber. In one embodiment the rubber is selected as onesuitable for footwear outsoles. Athletic footwear have rubber outsolesthat meet a variety of performance specifications. The outsoles aregenerally prepared from silica filled rubber compositions. To make therubber resins compatible with the filler and improve the physicalproperties, silane coupling agents are commonly used.

The compositions may further contain a metal compound such as oneselected from the group consisting of titanium or zirconium with one ormore alkoxy groups bonded to the titanium or zirconium. Mixtures of suchmetal compounds may also be used. In some embodiments, the zirconium ortitanium metal compound is a chelate. Although the curable rubbercompositions preferably contain reinforcing fillers such as silica, insome embodiments, the compositions are essentially lacking in silanecoupling agents. Mixtures of rubbers may also be used. Examples ofrubbers useful in the invention include, without limitation, naturalrubber such as those based on polyisoprene.

The rubber composition includes a curing agent such as a peroxide orsulfur compound. Conventional sulfur based curing agents may be used inthe compositions. Such curing agents are well known in the art andinclude elemental sulfur as well as a variety of organic sulfide,disulfide and polysulfide compounds. Examples include, withoutlimitation, vulcanizing agents such as morpholine disulfide,2-(4′-morpholinodithio)benzothiazole, and thiuram compounds such astetramethylthiuram disulfide, tetraethylthiuram disulfide anddipentamethylenethiuram tetrasulfide. The vulcanizing or curing agentsmay be used alone or in combination with each other. In a preferredembodiment, peroxide is used as the curing agent. The peroxide can beany organic peroxide that can decompose and yield free radicals capableof crosslinking the rubber resin. Typical methods used to induceperoxide decomposition to yield the free radicals include heat, visiblelight, ultraviolet light or other actinic radiation. For most rubbercompounds, heat is a preferred method of inducing decomposition becausethe rubber composition tends to be opaque. However, in the case of clearrubbers, UV and visible light may be used to initiate the decomposition.Nonlimiting examples of suitable peroxides include dicumyl peroxide,benzoyl peroxide, bis(4-methylbenzoyl) peroxide, diisopropylbenzoylperoxide, 1,1-di-(tert-butylperoxy)-3,3,5-trimethylcyclohexane,di-2,4-dichlorobenzoyl peroxide, and2,5-dimethyl-2,5-di-(tert-butylperoxy)hexane. The amount of curing agentused in the rubber formulation may be at least about 0.01, preferably atleast about 0.05 percent by weight of the rubber formulation. The amountof curing agent used in the rubber formulation may also be up to about1.5, preferably up to about 1.0, more preferably up to about 0.3 percentby weight of the rubber formulation.

The rubber compositions may also, in general, contain accelerators whensulfur is used instead of peroxide as the curing agent. Suchaccelerators and co-accelerators are known in the art and include,without limitation, those based on dithiocarbamate, thiazole, amines,guanidines, xanthates, thioureas, thiurams, dithiophosphates, andsulfenamides. Non-limiting examples of accelerators include: zincdiisobutyldithiocarbamate, zinc salt of 2-mercaptobenzothiazole,hexamethylenetetramine, 1,3-diphenyl guanidine, zinc isopropyl xanthate,trimethyl thiourea, tetrabenzyl thiuram disulfide,zinc-O—,O-di-n-butylphosphorodithiolate, andN-t-butyl-2-benzothiazylsulfenamide.

It may be desirable to provide rubber compositions that cure and can beprocessed with a minimum of emissions of potentially harmfulby-products. In some embodiments, it is preferred to use acceleratorsand co-accelerators that are non-nitrosamine generators ornon-carcinogenic nitrosamine generators. One such accelerator istetrabenzylthiuram disulfide. It is known to generate a non-carcinogenicnitrosamine, N-nitrosodibenzylamine, which is not known to becarcinogenic according to published literature. A preferredco-accelerator is MBTS or 2,2′-dithiobisbenzothiazole.

The rubber composition includes at least one kind of reactive speciesthat, under the molding conditions, forms a covalent bond between thecured rubber and the first thermoplastic composition by reaction with agroup present in the first thermoplastic composition. In one embodiment,the reactive species comprises a radical generated from the curing agent(peroxide or sulfur compound) for the rubber, which reacts with areactive group in the first thermoplastic composition selected fromunsaturated carbon bonds such as vinyl groups, carbonyl groups such asthose in urea, urethane, ketone, aldehyde, ester, and amide moieties,thiocarbonyl groups, cyano groups, epoxide groups or other strainedrings with heteroatoms, and reactive alpha hydrogens. In one particularexample, the first thermoplastic material comprises an additionpolymerizable unsaturated group that is covalently bonded to the rubberduring curing of the rubber. One such thermoplastic material containingpolymerizable unsaturation is a millable polyurethane.

In another embodiment, the reactive species of the rubber compositioncomprises a group of a compound other than a curing agent in the rubbercomposition that reacts with a functionality in the first thermoplasticcomposition. Examples of such compounds that may be included in therubber composition are amino functional silane coupling agents,described in more detail below, which have an amine group available forreaction with isocyanate, carboxyl, ester or amide groups in the firstthermoplastic composition and silane groups that react with metal oxidessuch as silica fillers in the rubber composition. Other coupling agentssuch as zirconates and titanates may also be used. For example acoupling agent having a labile hydrogen, for example from an aminegroup, can react with an isocyanate group of the thermoplastic resin orcan undergo a transesterification reaction with an ester or substitutionat the linking oxygen of a urethane group to form an amide or urea groupcovalent bond with the first thermoplastic material. In a variation ofthis, the coupling agents may be included in the first thermoplasticcomposition for these reactions.

In another embodiment, the rubber composition may include a small amountof addition polymerizable monomer with reactive species such ascarboxyl, anhydride groups, hydroxyl groups, isocyanate groups, epoxidegroups, and so on that are incorporated into the rubber by the curingreaction and provide functionality at the interface of the rubber andthermoplastic portions for covalent bonding with complementary reactivegroups in the first thermoplastic composition. Examples of suchpolymerizable monomers include, without limitation, vinyl monomers suchas esters of α,β-ethylenically unsaturated monocarboxylic acidscontaining 3 to 5 carbon atoms such as acrylic, methacrylic, andcrotonic acids and of α,β-ethylenically unsaturated dicarboxylic acidscontaining 4 to 6 carbon atoms; vinyl esters, vinyl ethers, vinylketones, vinyl aldehydes (enals), and aromatic or heterocyclic aliphaticvinyl compounds. Certain primary or secondary halo-functional alkanes oralkenes can be incorporated. It is also possible to incorporate a minoramount of a thermoplastic polymer that has such reactive species, suchas polyurethanes, alkyds, polyesters, polyamides, poly(ether amides),epoxy resins, acetals, SAN, SEBS, and so on having carboxyl, hydroxyl,epoxide, isocyanate, and amino groups, ethylenic unsaturation, and soon.

The rubber compositions generally contain reinforcing fillers. Suchfillers include silica, carbon black, clay, organic fiber, inorganicmetal powder, mineral powder, talc, calcium sulfate, calcium silicate,and the like. Silica is preferred in some embodiments. Typicalcompositions for use in preparing molded rubber outsoles for athleticshoes may contain about 10 to about 60 parts per hundred by weightfiller.

The rubber compositions may optionally contain a titanium or zirconiumcompound with at least one alkoxy group bonded to the metal atom, asdescribed in Wilson III, U.S. Pat. No. 6,620,871. Mixtures of thezirconium and titanium compounds of the invention may also be used.Generally, the R group of the alkoxy group is an alkyl group having 8 orfewer carbon atoms. In a preferred embodiment, the R group contains 6 orfewer carbons, and more preferably contains 4 or fewer carbon atoms.Examples of alkyl groups containing 4 or fewer carbon atoms includemethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, andt-butyl.

Preferably, the rubber compositions may also contain coupling agents,such as those based on silanes. When present, the silane coupling agentscontribute to the stability and physical properties of the compositions,for example, by compatibilizing or coupling the reinforcing filler withthe rubber components. Silane coupling agents include those with amino,epoxy, (meth)acryl, chloro, and vinylyl functionality.

Examples of amino functional silane coupling agents includeaminopropyltriethoxysilane; aminopropyltrimethoxysilane;aminopropylmethyldimethoxysilane; aminoethylaminopropyltrimethoxysilane;aminoethylaminopropyltriethoxysilane;aminoethylaminopropylmethyldimethoxysilane;diethylenetriaminopropyltrimethoxysilane;diethylenetriaminopropyltriethoxysilane;diethylenetriaminopropylmethyldimethoxysilane;diethylenetriaminopropylmethyldiethoxysilane;cyclohexylaminopropyltrimethoxysilane;hexanediaminomethyldiethoxysilane; anilinomethyltrimethoxysilane;anilinomethyltriethoxysilane; diethylaminomethyltriethoxysilane;(diethylaminoethyl)methyldiethoxysilane; andmethylaminopropyltrimethoxysilane. Examples of sulfur functional silanecoupling agents include bis(triethoxysilylpropyl)tetrasulfide;bis(triethoxysilylpropyl)disulfide; bis (3-ethoxydimethylsilylpropyl)oligosulfur; mercaptopropyltrimethoxysilane;mercaptopropyltriethoxysilane; mercaptopropylmethyldimethoxysilane; and3-thiocyanatopropyltriethoxysilane. Examples of epoxy silane couplingagents include: glycidoxypropyltrimethoxysilane;glycidoxypropyltriethoxysilane; glycidoxypropylmethyldiethoxysilane; andglycidoxypropylmethyldimethoxysilane. Examples of (meth)acryl silanecoupling agents include: methacryloxypropyltrimethoxysilane;methacryloxypropyltriethoxysilane; andmethacryloxypropylmethyldimethoxysilane. Examples of chloro silanecoupling agents include: chloropropyltrimethoxysilane;chloropropyltriethoxysilane; chloromethyltriethoxysilane;chloromethyltrimethoxysilane; and dichloromethyltriethoxysilane.Examples of vinylyl silane coupling agents include:vinyltrimethoxysilane; vinyltriethoxysilane; andvinyltris(2-methoxyethoxy)silane.

It has been found that compositions containing low levels ofnon-petroleum oils can produce molded articles for outsoles for athleticshoes having acceptable physical properties, even in the absence ofconventional silane coupling agents. Such compositions and moldedarticles produced from them may provide environmental and healthbenefits.

The rubber composition may include a colorant such as a pigment or dye.Nonlimiting examples of suitable colorants include organic and inorganicpigments. The amount of colorant used in the rubber formulation varieswidely, depending upon the specific colorant or colorants used and thecolor desired. The rubber composition may include one or more of variousother additives. Nonlimiting examples of suitable additives includeantioxidants, process aids, extenders, and tackifiers. Such additivesare generally included in amount of up to about 10% by weight of thetotal rubber composition.

The rubber compositions can be compounded in conventional rubberprocessing equipment. In a typical procedure, all components of therubber composition are weighed out. The rubber and additives are thencompounded in a conventional mixer such as a Banbury mixer. If desired,the compounded rubber may then be further mixed on a roller mill. Atthis time, it is possible to add pigments such as carbon black. Thecomposition may be allowed to mature for a period of hours prior to theaddition of sulfur and accelerators, or they may be added immediately onthe roller mill. It has been found to be advantageous to add theaccelerators into the Banbury mixer in the later stages of the mixingcycle. Adding the accelerators into the Banbury mixer generally improvestheir distribution in the rubber composition, and aids in reduction ofthe cure time and temperatures. In general, an elemental sulfur curingcompound is not added into the Banbury mixer. Organic sulfides (sulfurdonating compounds) may be added to the Banbury mixer.

The rubber composition may be formed into a sheet, typically bycalendaring or extrusion, for placement in the first mold. The rubbercomposition sheet is approximately the thickness desired for the molded,cured rubber layer. The rubber composition sheet may be at least about 2mm, preferably at least about 5 mm in thickness. The rubber formulationsheet may also be up to about 10 mm in thickness.

The rubber material may be foamed or blown by use of foaming or blowingagents as mentioned above.

The rubber composition is molded with a layer of the first thermoplasticcomposition, which will function as a tie layer to firmly attach themolded, cured rubber portion to a second thermoplastic composition. Thefirst thermoplastic composition includes one or more thermoplasticpolymers and may optionally contain additives such as pigments, fillers,antioxidants, process aids, extenders, coupling agents, silica, andtackifiers. While the polymer or polymers used in the firstthermoplastic composition are generally thermoplastic in the major partof the layer, it should nonetheless be apparent that in certainembodiments that will be described there may be some crosslinking ofthis layer at its interface with the rubber. Nonlimiting examples ofsuitable thermoplastic polymers include thermoplastic elastomers,polyurethanes, polyesters, polyamides, vinyl polymers including, withoutlimitation, copolymer of vinyl alcohol, vinyl esters, ethylene,acrylates, methacrylates, styrene, and so on, polyacrylonitrile,polyphenylene ethers, polycarbonates, and so on. Particularly usefulthermoplastic polymers include styrene-butadiene-styrene (SBS) blockcopolymers, styrene-ethylene butylene-styrene (SEBS) block copolymers,ether-amide block copolymers, and unsaturated or millable urethane (TSEM97).

In one embodiment, the first thermoplastic composition includes areducible chemical species susceptible to reaction with the curing agentof the rubber formulation. Nonlimiting examples of reducible chemicalspecies include ethylenically unsaturated groups such as vinyl groups,carbonyl groups such as those forming part of urea, urethane, ketone,aldehyde, ester, and amide groups, thiocarbonyl groups, cyano groups,epoxide or other strained-ring structures, and reactive alpha hydrogensand abstractable hydrogens such as those of the arylated methylenegroups of polyurethanes of 4,4′-methylenediphenylisocyanate (MDI) andalpha-methylene groups of adipate polyesters or polyester segments inpolyurethanes prepared from hydroxyl-terminated adipate polyesters.Other examples of suitable materials with reducible chemical speciesinclude SBS block copolymer, polyesters of maleic anhydride or otherunsaturated acids and polyurethanes prepared with suchhydroxyl-functional polyesters, and acrylated or methacrylated polymers.The first thermoplastic composition may include a colorant such as apigment or dye. Nonlimiting examples of suitable colorants includeorganic and inorganic pigments. The first thermoplastic composition mayinclude one or more of various additives such as fillers, antioxidants,process aids, extenders, tackifiers, plasticizers, and so on, but thefirst thermoplastic composition should be free from any initiator forfree radical polymerization (i.e., even when the first thermoplasticcomposition contains addition polymerizable moieties, it is not “cured”when the rubber is cured, instead reaction resulting in covalent bondingtakes place at the interface with the rubber composition).

The first thermoplastic composition may be formed into a sheet,typically by calendaring. In general, the first thermoplasticcomposition sheet will be substantially less thick compared to therubber portion of the first molded article. The first thermoplasticcomposition sheet should be thick enough to handle without tearing andthin enough to easily drape over the rubber The first thermoplasticcomposition sheet may be at least about 0.05 mm, preferably at leastabout 0.1 mm, more preferably at least about 0.2 mm in thickness. Thefirst thermoplastic composition sheet may also be up to about 1 mm,preferably up to about 0.5 mm, more preferably up to about 0.3 mm inthickness.

In one embodiment, the rubber composition sheet and first thermoplasticcomposition sheet are place adjacent one another, and the two layers aretogether die cut to a desired pre-form shape. The two die-cut layers arethen placed together, tie layer side up, in a mold and heated to curethe rubber formulation. In another embodiment, a pre-form shape of therubber composition and the first thermoplastic composition may be madeseparately and placed in the mold, or a perform of the rubber may beplaced in the mold and a layer of the first thermoplastic composition isintroduced by spraying, brushing, or rolling an amount of the firstthermoplastic composition or positioning a solid layer of the firstthermoplastic composition in the mold over the rubber pre-form.

The mold is placed into a press and held for a specified period of timeat a temperature sufficient to achieve cure. Typically, the curing timeis obtained from a rheometer curve, such as conventional in the rubberprocessing industry. For example, the moldable rubber compositions maybe cured for a time equal to T90 plus one minute, where T90 is the timerequired for 90% of the viscosity to develop. Typical temperatures aregenerally from about 145 to 165° C., and typical times can range from3-9 minutes, though processing outside these times and temperatureranges is also possible, especially in large parts with thick crosssections. The temperature of the mold depends upon the particular curingagent used in the rubber formulation, and typically may vary from about50° C. to about 300° C. The mold is closed under pressure and the tielayer of the first thermoplastic composition is co-molded with, andcovalently bonded to, the rubber layer during the curing cycle for therubber. The curing cycle may be, for example and without limitation,between 1 minute and 30 minutes in length depending on the thickness ofthe rubber layer. A ten-or fifteen-minute cycle is typical. During thecuring cycle, the unsaturated groups or other reactive groups of thefirst thermoplastic composition react with the rubber composition at theinterface of the two layers. When the reactive group of thethermoplastic composition is unsaturated carbon bonds, the amount ofcuring agent in the rubber must be sufficient to cause this interlayercrosslinking to take place so as to form a strong bond between the twolayers. In the case of an additive such as coupling agents, theconcentration of such additives at the interface must be high enough toform the desired bond strength.

The cured rubber insert having the first thermoplastic composition layerbonded on one side is removed from the rubber mold and transferred to asecond mold to be molded as an insert with a second thermoplasticcomposition. The thermoplastic, tie layer side faces up, into the voidof the mold where it will interface with the second thermoplasticcomposition. The mold can have a recessed cavity designed to accept theinsert. After placing the insert into the mold, the mold is closed andthe second thermoplastic material is injected into the mold to form anarticle comprising the insert.

The second thermoplastic composition molded with the insert may be anymaterial compatible with the thermoplastic material of the insert.Nonlimiting examples of useful thermoplastic polymer for injectionmolding include thermoplastic polyurethanes, polyamides such as thoseavailable under the product designations Rilsan, Grilamid, Vestamid, andso on, polyether-polyamide copolymers such as those available under theproduct designations Pebax or Daiamid, ethylene-vinyl alcohol copolymerssuch as the product available under the designation Levaprene, SEBS,SBS, PEEK, ABS, poly (ester-imide) copolymers, polyesters such aspolyesters sold under the designation Crastin. ester-ether blockcopolymers such as products sold under the designation Hytrel, and soon. The second thermoplastic composition may include any of thecolorants or additives already mentioned in connection with the firstthermoplastic composition. In some embodiments for footwearapplications, it is desirable to use polyamide 11, polyamide 12,polyester-based or polyether-based thermoplastic polyurethanes,polyamide 6, polyamide 66, PBT, PET, PEA6, or PEE6. When the moldedarticle is to be used as an outsole for footwear, typical additivesinclude fillers, antioxidants and other stabilizers, process aids,extenders, and tackifiers.

The molding temperature of the second molding step should besufficiently high to cause a melt fusion or weld and/or covalent bondingto form with the first thermoplastic layer of the insert. The polymersof the first thermoplastic composition layer and the secondthermoplastic composition may covalently bond when they containcomplementary reactive groups on polymers or other material in theirrespective compositions, such as epoxide groups in the one and carboxyl,amino, and/or hydroxyl groups in the other, or ester or urethane groupsin the one and hydroxyl an/or amino groups in the other. In anotherexample, the first thermoplastic composition may include a couplingagent having a labile hydrogen, for example from an amine group, thatcan react with an isocyanate group of the second thermoplastic resin orcan undergo a transesterification reaction with an ester or substitutionat the linking oxygen of a urethane group to form an amide or urea groupcovalent bond with the second thermoplastic material.

The thermoplastic with molded rubber inserts may, for example, be anoutsole for footwear. FIG. 1 illustrates shoe 2 having outsole 8.Outsole 8 is composed mainly of a thermoplastic material 4, but includesa number of rubber traction elements 6 located generally in the areas ofcontact for the sole surface of sole plate when the wearer of thefootwear stands. The traction elements 6 are ridged or embossed to gripthe contacted surface. The outsole is formed by the process describedabove, in which, in a first step, the rubber for the traction elementinserts is molded and cured in a first mold that introduces the ridgingor embossing on an outer surface and covalently bonds a firstthermoplastic material (tie layer) on an inner surface that will contactthermoplastic material 4 (the second thermoplastic material). Then, themolded rubber traction elements 6 are inserted into a second mold wherethe thermoplastic material 4 is added and molded to form the outsole 8.

The interfaces between rubber traction elements 6 and thermoplasticmaterial 4 are shown in FIG. 2. FIG. 2 is a cross-sectional view alongline 2-2, which passes through two rubber traction elements 6 of outsole8. Thermoplastic material 4 and rubber traction elements 8 are joined bya thermoplastic material in tie layer 10. Thermoplastic tie layer 10comprises a thermoplastic material that is compatible with thermoplasticmaterial 4, such that it is firmly bonded with thermoplastic material 4.Thermoplastic tie layer 10 has also formed covalent bonds at itsinterface with rubber traction elements 6. Rubber traction elements 6are thus firmly held in place in outsole 8. While thermoplastic layer 10and rubber traction element 6 are shown in FIG. 2 as having similarthicknesses, the thickness of thermoplastic layer 10 can actually bemuch less than that of rubber element 6.

FIG. 3A illustrates placement of a rubber segment 22 in an outsole 24 inan area underlying the toes to provide enhanced flexibility. Layers 23of the first thermoplastic material, are interposed as tie layersbetween rubber segment 22 and areas 28 of the second thermoplasticmaterial, with the layers 23 being covalently bound to rubber segment 22at their interface and being thermally welded or covalently bound, asshown in cross-section 3B taken along line D-D of FIG. 3A. FIG. 3C showsan alternative arrangement of the interfaces of the first thermoplasticmaterial 23 between rubber segment 22 and second thermoplastic materialareas 28, in which the first thermoplastic material 23 is incorporatedaround a perimeter portion of the rubber segment 22 of the flex grooveto improve interfacial strength between the elastic flex groove and therigid thermoplastic sole unit.

FIG. 4A illustrates an outsole having wedge-shaped rubber segments 22 a,22 b, 22 c bonded to thermoplastic outsole 26 through thermoplastic tielayers 23. The outsole is again made by the process described above, sothat at interfaces 28 tie layers 23 are covalently bonded to rubbersegments 22 a, 22 b, 22 c and at interfaces 29 tie layers 23 arethermally welded and/or covalently bonded to thermoplastic outsole 26.The wedge-shaped rubber segments 22 a, 22 b, 22 c provide enhancedflexibility of the footwear outsole 26 along lines B-B and C-C.Thermoplastic tie layers 23 ensure durable bonding between thermoplasticand rubber areas. In this embodiment, the first thermoplastic materialunderlies and edges the rubber segment set into the thermoplasticoutsole material. FIG. 4B shows a partial cross-section along line4B-4B, showing thermoplastic tie layers 23 lying between rubber segment22 a and thermoplastic outsole 26.

This description of my technology is merely exemplary in nature and,thus, variations that do not depart from the gist of the presentdisclosure are intended to be within the scope of the invention. Suchvariations are not to be regarded as a departure from the spirit andscope of the invention.

1. A composite polymer article comprising a thermoplastic polymerportion and a rubber portion, and therebetween a polymeric layer,wherein a material in the polymeric layer is covalently bound to therubber portion and the polymeric layer is thermally welded to thethermoplastic polymer portion.
 2. A composite polymer article accordingto claim 1, wherein there is covalent bonding between the polymericlayer and the thermoplastic polymer portion.
 3. A composite polymerarticle according to claim 1, wherein the covalent bonding comprisescarbon-carbon bonds.
 4. A composite polymer article according to claim1, wherein the thermoplastic polymer portion comprises a thermoplasticelastomer.
 5. A composite polymer article according to claim 1, whereinthe thermoplastic polymer portion comprises a member selected from thegroup consisting of unsaturated polyurethanes, SBS block copolymers,polyesters of unsaturated dicarboxylic acids and anhydrides, acrylatedpolymers, methacrylated polymers, and polyurethanes.
 6. A compositepolymer article according to claim 1, wherein the rubber portioncomprises a modifying agent comprising a member selected from the groupconsisting of hydroxyl groups, carboxyl groups, amino groups, estergroups, and ether groups; wherein the polymeric layer is covalentlybound to the rubber portion through covalent bonds formed by reaction ofthe member.
 7. A composite polymer article according to claim 1, whereinthe polymeric layer comprises a member selected from the consisting ofstyrene-butadiene-styrene (SBS) block copolymers, styrene-ethylenebutylene-styrene (SEBS) block copolymers, ether-amide block copolymers,and unsaturated polyurethane.
 8. A composite polymer article accordingto claim 1, wherein the thermoplastic polymer portion comprises a memberselected from the group consisting of thermoplastic polyurethanes,polyamides, polyether-polyamide copolymers, ethylene-vinyl alcoholcopolymers, styrene-butadiene-styrene (SBS) block copolymers,styrene-ethylene butylene-styrene (SEBS) block copolymers, PEEK ABS,poly(ester-imide) copolymers, polyesters, and ester-ether blockcopolymers.
 9. A composite polymer article according to claim 1, whereinthe material in the polymeric layer is covalently bound to the rubberportion through a coupling agent.
 10. A composite polymer articleaccording to claim 1, wherein the polymeric layer is covalently bound tothe rubber portion through bonds between rubber functionality andcomplementary reactive groups in the polymeric layer.
 11. A compositepolymer article according to claim 10, wherein the rubber functionalitycomprises a member selected from the group consisting of carboxylgroups, anhydride groups, hydroxyl groups, isocyanate groups, epoxidegroups, and combinations thereof.
 12. A composite polymer articleaccording to claim 1, wherein the polymeric layer comprises a reduciblespecies.
 13. A composite polymer article according to claim 12, whereinthe reducible species is a member selected from the group consisting ofethylenically unsaturated groups, thiocarbonyl groups, cyano groups,epoxde and other strained-ring structures, reactive alpha hydrogens,abstractable hydrogens, and combinations thereof.
 14. An article offootwear having an outsole, wherein said outsole comprises athermoplastic material and at least one rubber insert joined to thethermoplastic material through a polymeric layer, wherein at a firstinterface of the polymeric layer a material in the polymeric layer iscovalently bound to the rubber insert and at a second interface thepolymeric layer is welded to the thermoplastic material.
 15. An articleof footwear according to claim 14, wherein there is also covalentbonding between the polymeric layer and the thermoplastic material atthe second interface.
 16. An article of footwear according to claim 14,wherein the rubber insert is a traction element of the outsole.
 17. Anarticle of footwear according to claim 14, wherein said covalent bondingcomprises carbon-carbon bonds.
 18. An article of footwear according toclaim 14, wherein the thermoplastic material comprises a thermoplasticelastomer.
 19. An article of footwear according to claim 14, wherein thethermoplastic material comprises a member selected from the groupconsisting of unsaturated polyurethanes, SBS block copolymers,polyesters of unsaturated dicarboxylic acids and anhydrides, acrylatedpolymers, methacrylated polymers, and polyurethanes.
 20. An article offootwear according to claim 14, wherein the rubber insert comprises amodifying agent comprising a member selected from the group consistingof hydroxyl groups, carboxyl groups, amino groups, ester groups, andether groups; wherein the polymeric layer is covalently bound to therubber insert through covalent bonds formed by reaction of said member.21. An article of footwear according to claim 14, wherein the rubberinsert is foamed.
 22. An article of footwear according to claim 14,wherein the rubber insert comprises a member selected from theconsisting of hydroxyl groups, carboxyl groups, amide groups, aminogroups, thiol groups, isocyanate groups, epoxide groups, silane groups,urethane groups, ester groups metal carboxylate groups, and anhydridegroups; wherein the polymeric layer is covalently bound to the rubberinsert through covalent bonds formed by reaction of said member.
 23. Anarticle of footwear according to claim 14, wherein the polymeric layercomprises a member selected from the consisting ofstyrene-butadiene-styrene (SBS) block copolymers, styrene-ethylenebutylene-styrene (SEBS) block copolymers, ether-amide block copolymers,and unsaturated polyurethane.
 24. An article of footwear according toclaim 14, wherein the polymeric layer is from about 0.05 mm to about 1mm thick.
 25. An article of footwear according to claim 14, wherein thethermoplastic material comprises a member selected from the groupconsisting of thermoplastic polyurethanes, polyamides,polyether-polyamide copolymers, ethylene-vinyl alcohol copolymers,styrene-butadiene-styrene (SBS) block copolymers, styrene-ethylenebutylene-styrene (SEBS) block copolymers, PEEK ABS, poly(ester-imide)copolymers, polyesters, and ester-ether block copolymers.
 26. An articleof footwear according to claim 14, wherein the rubber insert increasesflexibility of the outsole.
 27. An article of footwear according toclaim 14, wherein the thermoplastic material comprises a groove in whichthe rubber insert is set, having the polymeric layer located around aperimeter portion of the rubber insert set into the groove.
 28. Anarticle of footwear according to claim 14, wherein the rubber insert iswedge-shaped.